Memory cards are widely used with electronic devices, especially with portable consumer devices such as PDAs, Cameras, mobile phones et al. Card connectors for connecting the memory cards to the electronic devices usually have switch means for detect presence of the memory cards. Since the electronic devices are required to be more and more small in size, the memory cards are desired to be smaller too, and so do the card connectors. Sensitive detection of the small cards is a task for designer of the card connectors.